Help find x. I believe it’s 13

Answer:
m∠RST = 155°
m∠RSU = 102°
Step-by-step explanation:
m∠RST = m∠RSU + m∠UST
12x - 1 = 9x - 15 + 53
12x - 9x = 1- 15 + 53
3x = 39
x = 39/3
x = 13°
m∠RST = (12x -1)° = (12 * 13 - 1)° = (156 - 1 )° = 155°
m∠RSU = (9x -15)° = (9 * 13 - 15)° = ( 117 - 15)° = 102°